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    CWG Issue 505</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="505"></A><H4>505.
  
Conditionally-supported behavior for unknown character escapes
</H4>
<B>Section: </B>5.13.3&#160; [<A href="https://wg21.link/lex.ccon">lex.ccon</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD1
 &#160;&#160;&#160;

 <B>Submitter: </B>Mike Miller
 &#160;&#160;&#160;

 <B>Date: </B>14 Apr 2005<BR>


<P>[Voted into WP at the October, 2006 meeting.]</P>

<P>The current wording of 5.13.3 [<A href="https://wg21.link/lex.ccon#3">lex.ccon</A>] paragraph 3
states,</P>

<BLOCKQUOTE>

If the character following a backslash is not one of those specified,
the behavior is undefined.

</BLOCKQUOTE>

<P>Paper J16/04-0167=WG21 N1727 suggests that such character escapes
be ill-formed.  In discussions at the Lillehammer meeting, however,
the CWG felt that the newly-approved category of
conditionally-supported behavior would be more appropriate.</P>

<P><B>Proposed resolution (April, 2006):</B></P>

<P>Change the next-to-last sentence of 5.13.3 [<A href="https://wg21.link/lex.ccon#3">lex.ccon</A>] paragraph 3
from:</P>

<BLOCKQUOTE>

If the character following a backslash is not one of those specified,
the behavior is undefined.

</BLOCKQUOTE>

<P>to:</P>

<BLOCKQUOTE>

Escape sequences in which the character following the backslash is not
listed in Table 6 are conditionally-supported, with
implementation-defined semantics.

</BLOCKQUOTE>

<BR><BR>
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